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5 causes of sudden knee pain without injury, according to our physical therapists

  • Writer: Performance Rehab KC Team
    Performance Rehab KC Team
  • Oct 2, 2025
  • 4 min read

Knee pain can make even the simplest of tasks more challenging, including walking, sitting or climbing stairs. About 25% of adults experience frequent knee pain and face these common struggles. When knee pain occurs after an injury, the cause is usually apparent. However, many people experience knee pain out of nowhere and cannot identify the cause. 


Whether you know what brought on your knee pain or have no idea, physical therapy is a great option when you’re looking for relief. A licensed physical therapist can help you pinpoint the cause and personalize a treatment plan based on your needs. Physical therapy can help you alleviate chronic pain and inflammation, improve your range of motion, and do your daily activities more easily.


Let’s explore five causes of sudden knee pain without injury and how physical therapy may help you feel better.


5 causes of sudden knee pain without injury


Experiencing knee pain without knowing what caused it can be frustrating. An underlying condition, inflammation or overuse could be the culprit, but you may not be able to determine this on your own. Identifying the cause is the first step toward getting treatment that can help provide you with the relief you need, and physical therapists are experts in the musculoskeletal system.


Here are five common causes of knee pain that can occur suddenly without an injury:


  1. Tendinitis


Tendinitis is inflammation of the tendons that attach muscle to bone, which can occur from overusing the tendons in the knee. Frequent running, jumping, climbing stairs or playing sports can cause this inflammation and chronic pain. 


Common symptoms of tendinitis include:


  • Pain located just below the kneecap

  • Pain that worsens with physical activity

  • Swelling, tenderness and redness

  • Difficulty extending the knee completely


  1. Arthritis


There are over 100 different types of arthritis, which is a condition that causes inflammation in the joints. Not every type of arthritis has the same cause. Over time, cartilage can wear down, which may lead to this condition. Rheumatoid arthritis is believed to be an autoimmune disorder, occurring when the body’s immune system mistakenly attacks healthy joints. Genetics, age and obesity are other potential causes.


Common symptoms of arthritis include:


  • Aches, pain and stiffness in the joints

  • Difficulty moving the affected joints

  • Cracking or grinding noises and sensations when moving joints

  • Stiffness that worsens with inactivity


  1. Bursitis


Bursae are small sacs full of fluid that lubricate and cushion the joints, and bursitis can occur when bursae become inflamed. Overuse, repetitive movements, infections and certain medical conditions like arthritis may trigger this condition.


Common symptoms of bursitis include:


  • Dull, sharp, or throbbing pain in the affected joint

  • Limited range of motion

  • Popping or cracking sounds in the joint

  • Pain that worsens at night


  1. Osgood-Schlatter disease


This condition is the inflammation of the patellar tendon below the knee. Repetitive stress on this tendon can cause Osgood-Schlatter disease. Excessive running or jumping and frequently climbing stairs may lead to this painful condition.


Common symptoms of Osgood-Schlatter disease include:


  • Pain below the kneecap

  • Tenderness, swelling and weakness

  • Difficulty walking or running 

  • Pain that worsens with activities like running, kneeling and jumping 


  1. Baker’s cyst


A Baker’s cyst is a fluid-filled sac that can develop and cause pain behind the knee. Typically, an underlying condition may cause a Baker’s cyst, and it can develop after the onset of arthritis. While some people don’t experience any symptoms, others may feel symptoms ranging from pain to difficulty moving. 


Common symptoms of Baker’s cyst include:


  • Aching or dull pain behind the knee

  • Difficulty straightening or bending the knee

  • Warmth, redness, numbness or tingling 

  • A lump behind the knee

  • Limited range of motion


How physical therapy can help


Regardless of what condition you may have, you can always contact a physical therapist for help. They can assess your knee and pinpoint the cause of your pain, and once it has been identified, your condition can be much easier to treat. 


Your physical therapist may guide you through therapeutic exercises to strengthen your knee, improve flexibility and enhance range of motion. In the process, you may experience the pain relief you’re looking for in addition to being able to do your daily routine more easily. If you’ve been struggling with chronic pain, limited range of motion or difficulty doing regular activities, it may be time for expert support.


Performance Rehab can help your knee pain


Whether your chronic knee pain has just begun or you’ve had it for a while, it’s never too late to get treatment. Even if you don’t know the cause, an expert can work with you to identify it and provide a personalized plan that can help you feel better. Under the guidance of a licensed physical therapist, you can learn exercises that can help alleviate your pain and inflammation while improving your range of motion. At Performance Rehab, our team can support you and help make your daily activities easier to do.


Ready to ditch the discomfort and get moving again? Connect with our experienced rehab specialists and take the first step toward a healthier, more active life. Request an appointment or contact us to get started.

 
 
 
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